Methods and apparatus for casting ceramic sheets

A method for making a thin, free-standing ceramic sheet, the method comprising:

• drawing a carrier film proximate a casting head and across a casting bed of a tape caster at a rate from about 2 cm/min to about 500 cm/min;
• depositing a thin film of ceramic slip on the carrier film with the casting head, wherein the thin film of ceramic slip deposited on the carrier film is less than about 150 μm thick and greater than about 15 cm wide and comprises ceramic powders with an ultimate crystallite size of less than about 10 μm dispersed in a fluid vehicle such that the ceramic slip has a ceramic solids fraction of at least about 20 wt. %
• drying the ceramic slip deposited on the carrier film as the carrier film is drawn through a drying chamber of the tape caster to form a green ceramic sheet on the carrier film, wherein the drying chamber is maintained at a temperature of less than about 150° C. as air is passed through the drying chamber at a rate from about 40 ft./min to about 3,000 ft./min;
• and
• sintering the green ceramic sheet on roughened setters wherein no extra weight is placed on the green ceramic sheet during sintering wherein:
• the casting head comprises a slot die comprising a slot gap which may be adjusted from about 25 μm to about 250 μm;
• the slot die is spaced apart from the carrier film by less than about 300 μm and comprises an angular orientation of about −25 degrees to about 25 degrees relative to horizontal;
• and
• the ceramic slip is delivered to the slot die with a slip metering device comprising a gear pump such that the ceramic slip is deposited on the carrier film at a rate from about 0.01 ml/cm/min to about 2.2 ml/cm/min.